<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <form action="">
        <style>
        *{
            border: 1px solid red;
        }
        </style>
        <p>段落</p>
        <b>加粗</b>
        <span>无</span>

        <style>
        p{
            color: red;
        }
        </style>
        <p>段落</p>
        <style>
        #abc{
            font-size: 20px;
        }
        </style>
        <p id="abc">段落</p>
        <style>
        .abc{
            border: 1px solid red;
        }
        </style>
        <b class="abc">加粗</b>
        <span class="abc">无</span>
        <style>
        b.abc{
            border: 1xp solid red;
        }
        </style>
        <span class="abc edf">无</span>

        <style>
        [href]{
            color: orange;
        }
        </style>
        <style>
        [type="password"]{
            border: 1px solid red;
        }
        </style>
        <style>
        [href^="http"]{
            color: orange;
        }
        </style>
        <style>
        [href$="http"]{
            color: orange;
        }
        </style>
        <style>
        [href*="baidu"]{
            color: orange;
        }
        p,b,i,span{
            color: red;
        }
        p b{
            color: red;
        }
        ul>li{
            border: 1px solid red;
        }
        </style>
        <ul>
            <li>
                <ol>
                    <li>我是</li>
                    <li>我是</li>
                </ol>
            </li>
            <li>我</li>
            <li>我</li>
        </ul>
        <style>
        ::first-line{
            color: red;
        }
        a::before{
            content: -请进;
        }
        </style>
    </form>
</body>
</html>